Instancing not working the way I want it to
You need to rotate the tentacle in Edit Mode so it aligns properly.  


  Orientation of the tentacle was adapted to the vertex normals of the parent mesh
   (tentacle was rotated -90° around the X axis in Edit Mode).  
  
  From Blender Manual


Step 01 - Set up Parenting



Step 02 - Rotate tentacle in Edit mode. I changed pivot point to 3D cursor for this.